The embodiment relates to a wireless power transmission technology. More particularly, the disclosure relates to a method of controlling transmission power depending on the coupling states between a wireless power transmitter and a wireless power receiver to maximize the power transmission efficiency.
A wireless power transmission or a wireless energy transfer refers to a technology of wirelessly transferring electric energy to desired devices. In the 1800's, an electric motor or a transformer employing the principle of electromagnetic induction has been extensively used and then a method for transmitting electrical energy by irradiating electromagnetic waves, such as radio waves or lasers, has been suggested. Actually, electrical toothbrushes or electrical razors, which are frequently used in daily life, are charged based on the principle of electromagnetic induction. The electromagnetic induction refers to a phenomenon in which voltage is induced so that current flows when a magnetic field is varied around a conductor. Although the commercialization of the electromagnetic induction technology has been rapidly progressed around small-size devices, the power transmission distance thereof is short.
Until now, wireless energy transmission schemes include a remote telecommunication technology based on magnetic resonance and a short wave radio frequency in addition to the electromagnetic induction.
Recently, among wireless power transmitting technologies, an energy transmitting scheme employing resonance has been widely used.
However, according to the energy transmitting scheme employing resonance according to the related art, the power transmission efficiency may be varied depending on the coupling states between the wireless power transmitter and the wireless power receiver.
Therefore, a scheme of maximizing the power transmission efficiency by reflecting the coupling state between the wireless power transmitter and the wireless power receiver is required.